Use the force
If you practice jhāna correctly according to the suttas, the force is always with you and it grows exponentially.
The jhān-o-meter: why should you use the force? because it's tangible proof of passadhi sambojjhanga
Stories of jhanic force
General principles of meditation
Why Chinese meditation masters (Buddhism and Taoism) tell you to touch tongue to roof and teeth don't touch
🔗📚: collection of articles for an eventual book, "Jhāna Passaddhi Baselines"